US2012/0035246 discloses a method for producing a single-stranded nucleic acid molecule capable of suppressing the expression of a target gene, and, as a monomer used for its production, production of a compound represented by formula (3)
(hereinafter referred to as the compound (3)) and its enantiomer is described in Example A3.
However, when the compound (3) obtained by the method described in US2012/0035246 is used, the yield of the single-stranded nucleic acid molecule is not necessarily sufficient.